Paid up letter

I have a Old Mutual account with Shapiro and the it's been now paid up I am still awaiting for a paid up letter which they promised to send after 21days from 5 March 2020.Instead I get threating emails that my account is not paid up yet I have spoken to more than 5 consultants followed by emails they told me not worry they still waiting for Old mutual to send me the letter. They don't even have the decency to keep me on the loop after all the promises they have made. I must say I am disappointed by the service it's very poor I cannot move on with my life because of the letter that takes more 21 days.